1. Field of Invention
This invention pertains to method and apparatus for recording and reading information stored in helical stripes on magnetic tape, and particularly to method and apparatus for using dual channels to record and read information stored in helical stripes on magnetic tape.
2. Prior Art and Other Considerations
Numerous prior art patents teach the recording and reading of information stored in helical stripes on magnetic tape. In a helical scan arrangement, travelling magnetic tape is partially wrapped around a rotating drum so that heads positioned on the drum are contiguous to the drum as the drum is rotated. A write head on the drum physically records data on the tape in a series of discrete stripes oriented at an angle with respect to the direction of tape travel. The data is formatted, prior to recording on the tape, to provide sufficient referencing information to enable later recovery during readout.
Among such prior art teachings are the following United State's Patents, all commonly assigned herewith and incorporated herein by reference:
(1) U.S. Pat. No. 4,843,495 to Georgis et al., entitled CYCLICAL SERVO ZONE TRACKING METHOD AND APPARATUS FOR HELICAL SCAN RECORDING DEVICES;
(2) U.S. Pat. No. 4,835,638 to Hinz et al., entitled APPARATUS AND METHOD FOR FORMATTING AND RECORDING DIGITAL DATA. ON MAGNETIC TAPE; and,
(3) U.S. Pat. No. 4,845,577 to Georgis et al., entitled APPARATUS AND METHOD FOR ENABLING RAPID SEARCHING OF HELICALLY RECORDED MAGNETIC TAPE.
Existing helical scan systems employ a single channel read/write configuration on the rotating drum, where the drum has a write head and a read head mounted 180 degrees apart. On each rotation of the drum, the first head writes the data track and the second head performs a read-back check to verify the written data. The write and read functions must occur exclusively due to the problems of crosstalk in the rotating drum and an associated rotary transformer. Existing single channel helical scan systems thus have a limited rate ("data transfer rate") at which information can be written and read.
Accordingly, it is an object of the present invention to provide an helical scan system which enhances the data transfer rate of a digital helical scan recorder.
An advantage of the present invention is the provision of a helical scan system which allows the capacity of a given length of tape to be increased by decreasing the track pitch.
A further advantage of the present invention is the provision of a helical scan system which is compatible with a single channel system.
Yet another advantage of the present invention is the provision of a helical scan system which does not suffer from crosstalk problems.